FD7
This is obviously a very important decision for you and you should consider all of the potential implications before making a decision.
Regarding quality of life on the 330. It's not great at the moment with limited layovers and lots of night turnaround flights. As you said, things can change but planning for the worst case helps in managing expectations. It is possible that you could be stuck on the 330 until the end which is supposed to be around 2017. Then you'll probably be sent to to the A380 fleet, which is a great place to be. However, at the moment you need 2500 on type to be eligible for a 380 command. We are talking potentially many years before you get back to the left seat based on the path outlined.
EK isn't a terrible company to work for. It's gotten a lot worse recently and probably will decline further in the future. But there are definitely worse places to work out there. The bottom line is that your decision to stay or join EK is a personal one and nobody can make that decision for you. If you're happy where you are and your airline is stable with good career prospects then perhaps you should stay. If the opposite is true and you don't mind dealing with some of the possibilities I've mentioned above, then by all means come.
Good luck in your choice whichever way it goes. Just make sure that your decision is made with your eyes wide open so that the regrets will be minimized down the road.